First of all, the new concept book is too simple, and the fourth book is not suitable for level 4, and level 6 is the level of the fourth book.

I have used the mobile version of the new concept, not only for explanation, translation, but also for word learning. You can look it up online.

New concept mobile version, because I don't know whether you are iphone or Android, I won't send it. Full, with articles and listening. They are all read by foreigners, and their pronunciation is very standard.

Vocabulary: I suggest you buy the New Oriental Level 4 vocabulary book, and pay attention to the one sorted by frequency, which will be much faster.

Website, because I can't type it out for you, so I said check it yourself, Pute English Listening Network, which not only has listening. Very good, very powerful.

And longbo. Com, where you can create a four-level vocabulary book, but some functions are charged.

Finally, CET-4 and CET-6, words are very important, reading is very important and listening is very important. Moreover, it is very important to do the real questions, because only the real questions are the real difficulty of CET-4 and CET-6, and other materials are either on the high side or on the low side, so it is impossible to grasp them at all, and the general direction of the questioner is not allowed. Ok, that's all, I hope it can be adopted.

Ps If you have any questions, please feel free to trust me personally. I have passed CET-4 and CET-6, and now I am taking gre and TOEFL.